Chain - The Block Chain API for Developers
Typehut - Super simple publishing platform
Opta - Opta is a new kind of Infrastructure-As-Code framework designed for fast moving startups.
Frost - An open API for Blockchain timestamping
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.
Telescope - Telescope is an open-source app that lets you easily set up your own online community.